This invention relates to foil-covered plastic parts and method of making such parts and, in particular, to foil-covered plastic parts and methods of making such plastic parts utilizing a hot stamping machine.
Typically, plastic parts are painted after they are molded. The painting process requires elaborate facilities and consequently necessitates large expenses. For instance, significant square footage of a factory must be dedicated to a clean room environment for the spraying of paint and clear coat and for the baking and curing of paint on components, such as those components used in the automotive industry, such as body panels, air bag covers, instrument panels and the like. Moreover, solvent-based paints have in recent years raised significant environmental concerns because of the volatile organic components which are emitted into the air during the application of such solvent-based paints. As a result, the evaporation of such solvents must be strictly monitored to satisfy environmental and safety regulations.
In addition, automotive components, especially interior automotive components, are strictly scrutinized following the painting process in order to match or conform the automotive component to the styling and aesthetic requirements of the associated interior trim product. Painting such automotive components following the molding process, raises quality concerns with respect to the color, consistency, and thickness of each individual paint application.
U.S. Pat. No. 4,902,557, the Rohrbacher reference discloses a method and apparatus for manufacturing a thermoplastic polyolefin composite useful as an exterior auto or truck body part.
U.S. Pat. No. 4,769, 100, the Short reference, teaches a method of applying a carrier film pre-printed with metallic paint to an automobile body panel in a vacuum forming process.
U.S. Pat. No. 4,952,351 and U.S. Pat. No. 5,466,412, the Parker patents, teach a method of manufacturing an air bag cover for an inflatable air bag system including a bond able film carrier, which is painted after the film carrier is molded.
Hot stamping is utilized for plastic decorating. For example, U.S. Pat. No. 5,769,548 discloses a hot stamp imprinting system with latchable ink ribbon cassette and handle.
However, the prior art fails to provide a foil-covered plastic part and method of making same wherein hot stamping is used and wherein the foil is bonded to the plastic part so as to have the durability and strength necessary to support varying applications.
An object of the present invention is to provide a foil-covered plastic part and method of making same wherein decorative features formed on an outer surface of the plastic part such as raised letters, scripts, logos, etc. are foiled to present an aesthetically pleasing appearance.
In carrying out the above object and other objects of the present invention, a foil-covered plastic part is provided. The foil-covered plastic part includes a plastic structural substrate having an outer surface and a decorative preform bonded to the outer surface. The preform has at least one foil-receiving portion formed in a plastic outer surface thereof. The foil-covered plastic part also includes a hot stamping foil having a foil top layer disposed on a plastic bottom layer which, in turn, is bonded to the plastic outer surface of the at least one foil-receiving portion to form the foil-covered plastic part.
The at least one foil-receiving portion may include a plurality of raised design portions having top and side surfaces and wherein the foil layer completely covers the top surfaces but not the side surfaces of the raised design portions.
The raised design portions may represent graphical information.
The decorative preform preferably comprises a plastic film sheet compatible with the plastic of the substrate so that fusion occurs between the plastic film sheet and the outer surface of the substrate. The plastic film sheet is shaped correspondingly to the outer surface of the substrate.
The plastic film sheet is preferably covered with a layer of acrylic color and polyvinylidine fluoride and an acrylic clear coat layer and wherein the plastic layer of the hot stamping foil is compatible with the acrylic clear coat layer so that diffusion occurs therebetween.
In one embodiment, the foil layer is a chrome layer.
In the embodiment shown, the substrate is a plastic front panel of an automotive air bag cover adapted to enclose an uninflated automotive air bag.
Still further in carrying out the above object and other objects of the present invention, a method is provided for making the foil-covered plastic part. The method includes providing a film sheet, vacuum molding the film sheet in a mold cavity to obtain a decorative preform having plastic top and bottom surfaces, and placing the decorative preform in a mold cavity of an injection mold having a shape defining the part. The method also includes injecting a thermoplastic elastomer into the mold cavity of the injection mold to generate a substrate of the part wherein the generation of the substrate of the part creates sufficient pressure and heat to bond the substrate to the bottom surface of the decorative preform and to form at least one foil-receiving portion at the plastic top surface of the preform. The method also includes the steps of providing a hot stamping foil having a foil top layer disposed on a plastic bottom layer, aligning the hot stamping foil with the at least one foil-receiving portion in a hot stamping machine, and operating the hot stamping machine for a time sufficient to generate a temperature and a pressure sufficient to melt and combine the top surface of the at least one foil-receiving portion and the plastic bottom layer of the hot stamping foil to form the foil-covered plastic part.
Important advantages of hot stamping are:
Dry Decorating Methodxe2x80x94There is clean-up required with hot stamping. A hot stamped part is immediately ready for handling and packaging.
Variety of Materialsxe2x80x94A variety of materials can be decorated using the hot stamping process. The most commonly decorated material is thermoplastics, but thermosets as well as wood, book cloth, leather, textiles, paper, cardboard and pre-painted metals are stamped with great success.
Variety of Decorating Finishesxe2x80x94Hot stamping is a decorative method where permanent gold and silver metallic graphics can be produced. Foils are also manufactured in gloss or matte pigment colors, wood grain designs, brushed effects, and chromium for exterior use. Multi-colored graphics can also be accomplished with pre-printed heat transfers and continuous patterned foils.
Variety of Surface Geometriesxe2x80x94Hot stamp foils can be applied to a variety of surface geometries including flat, cylindrical and spherical shaped parts along with raised beads graphics.
Minimum Set-Up Timexe2x80x94To change the stamping color simply involves changing a dry roll of hot stamp foil.
Permanent Decorationxe2x80x94Hot stamping foil has excellent adhesion and abrasion resistance due to thermal bonding that takes place.
EPA or Fire Safety Considerationsxe2x80x94With hot stamping, there are no EPA or fire safety considerations to be concerned about. Hot stamping, unlike other decorating methods, does not require any special storage, insurance or removal of hazardous solvents or vapors.
The above object and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.